Sleep disruptions increase during mid-life in women, due in part to the effects of age itself, but also possibly due in part to the menopausal transition, i.e.changes in hormones, symptoms, and bleeding that occur during the menopausal transition. The current, revised proposal (Sleep II) will extend longitudinally the currently funded, multi-site, multi-ethnic cross-sectional study of sleep in midlife women (Sleep I). In Sleep I, field-based examinations were conducted with 370 midlife pre-, peri- and postmenopausal Caucasian, African-American, and Chinese women from four of seven study sites from the Study of Women's Health Across the Nation (SWAN, a longitudinal study of menopause and aging), using in-home polysomnography, daily diaries and actigraphs, and self-report sleep questionnaires. In Sleep II, using a Coordinated R01 mechanism, a second field-based examination will be conducted on the same sample of women (who will be aged 51-62 years), incorporating the same procedures. A widely-cited heuristic model of the pathophysiology of sleep disturbances will be applied to these longitudinal data to evaluate the development of menopause-related sleep disturbances in this multi-ethnic sample of women. This model attributes acute sleep disturbances to the combined effects of predisposing and precipitating factors, and persistence of chronic sleep disturbances beyond the acute stressor to perpetuating factors. The specific aims for this longitudinal assessment of sleep through the menopausal transition are to identify potential: 1) predisposing factors (race, low socioeconomic status, low levels of physical activity, high body mass index, smoking, history of sleep problems, poor health status); 2) precipitating factors (vasomotor symptoms, new adverse life events, rapid increases in follicle stimulating hormone) for acute sleep disturbances during the transition; 3) perpetuating factors (poor sleep hygiene, dysfunctional attitudes and beliefs about sleep, heightened cognitive and physiologic arousal at night, race) for chronic sleep disturbances during the transition; and 4) adverse effects of sleep disturbances on subsequent health status during the early postmenopause (worsening metabolic profile and quality of life, increased hypertension, physical limitations). The public health relevance of this research is to understand better the changes in the sleep of women from different racial and socioeconomic backgrounds and identify risk factors for sleep problems. The results can inform primary prevention of adverse health outcomes due to the menopause-related sleep disturbances.